There are contact smart cards with interface terminal blocks, smart cards without contacts with an antenna housed in the carrier medium and hybrid cards or combicards which have an interface terminal block and an antenna.
There are numerous methods for making smart cards with contacts. Most of these methods are based on assembly of the chip in a sub-set called a micromodule which is assembled using traditional methods.
One method, illustrated in FIG. 1, involves first attaching the chip or microcircuit 20 (“die attach”) which involves gluing a chip 20, cut from a board by sawing, arranging it with its active side having its exit hubs 22 facing upwards and by sticking the opposite side on a dielectric support plate 28, using a glue which could be conducting, the gluing being done on a printed circuit or film.
Then microcabling or soldering of connections is done (“wire bonding”), involving soldering the connection of the exit hubs 22 of the chip 20 with the terminal block of contacts 24 of the printed circuit plate. Then the case is coated (“potting”), involving protecting the chip 20 and the soldered connection wires 26 using a resin 30 which could be silicone or polyurethane based, for example.
In a variation of this method illustrated in FIG. 2, a peripheral metallic ring 32 is used around the resin 30 to make the micromodule more rigid.
In another variation of this method (“flip chip”), a chip with bumps or protuberances placed with the active side downward is used, the electrical connection being provided either by metallic or polymer bumps or by an anisotropic adhesive.
In other variations, tape automated bonding (TAB) is used, as illustrated in FIG. 3, according to which the chip 34 is glued using an anisotropic glue 36 and the various contacts of the film 38 are soldered by thermocompression on the chip 34 which has bumps 39.
There are also methods for making smart cards with contacts without using micromodules. One method is based on using screen printing to form contacts and to provide chip interconnections.
Another method involves metallization in three dimensions of the body of the card, followed by transfer of the chip using classic technology (gluing plus microcabling) or by the “flip chip” technique described above.
In the methods which use a micromodule, the associated costs are limited by the price of the film. In addition, it is often necessary, after the encapsulation operation, to mill the resin to reduce the thickness of the unit. This operation is difficult because the resin is polymerized and thus very rigid. The milling is the main cause of production rejects.
In the first method without micromodules described above, this resin is on the surface and thus subject to exterior stresses, greatly increasing the associated cost. For the second method without micromodules the number of steps is high, which also increases the cost.
This technology would therefore not be suitable for making large chip cards.
There are two large families of methods for making smart cards without contacts. The first uses a wound antenna which is either soldered on a micromodule containing the chip, or directly on a chip with bumps. Such a technique can only be used for chips with simple operation.
The second family uses a “flat” antenna which can be in the form of a rectangular peripheral spiral or any other appropriate form. Such an antenna can be made by photogravure, mechanical cutting, stamp printing, screen printing, or offset printing with a conducting ink. The chip is then transferred to the antenna using the “flip-chip” technique or a classic technique.
In these methods for making smart cards without contacts, micromodule manufacturing is used which, as mentioned above, involves numerous steps for assembling the chip and implies substantial costs, or the “flipchip” technique for which the pace is limited and the installation costs particularly high.
The methods for hybrid smart cards combine the disadvantages previously mentioned for smart cards both with and without contacts.